C15 CAT head question...

Some of the differences I have seen is that between the 5EK and 6NZs are the oil returns that you already pointed out, and there are releif cuts in the 6NZs head between each cylinders that 5EK didnt have, the only difference I noticed on the acerts are all the fittings are Oring instead of pipe thread.

There are more qualified techs on here should chime in

 

You CAN use an acert head on a 3406E but there isn't much point. There will be extra bolt holes for the IVA's that you won't use and they cost more (like $1000 more). As far as the relief cuts GP1500SC pointed out, they're all going to have them regardless of which you choose. If you have a flat head now with no relief cuts IMO i would hang on to it and just have it checked by a machine shop. There are guys looking for those old heads. In my opinion if you end up replacing the head buy a NEW head, not a reman. It's been my experience that its worth the extra money.

 

Eustace I have the original head from a 2002 6NZ. It has only 250,000 miles on it. It has some rust issues because the man I bought the engine from had let it get a
significant amount of water in it i.e. stored outside and uncovered. Depending on the money numbers I would consider selling this head and buying a new one for my project. I did not realize that the older type head was worth something more than normal. If you know someone interested in it, pm me. I will have it checked relief cuts. I was going to use it but the man doing the build recommends getting another head.

 

Don't waste your time with this head it will have the cuts.